Prospective neighbors of wind turbines heard all the promises: “Quiet as a library.” “Like a baby’s breath.” “The same decibel level as a refrigerator.” The more brazen wind developers claimed “you will not hear them.” Then the four hundred and fifty foot wind towers with their bus-size nacelles and three-bladed fans were built. Sixteen in Sheffield, four on Georgia Mountain, twenty-one in Lowell. And neighbors learned the truth. Yes, you can hear them. They sound like “a jet plane that never lands,” or “sneakers in a drier,” or there is a “thump thump thump” or a “whoosh whoosh whoosh” as the blade passes the tower, causing something called amplitude modulation.
“If the noise was the same all the time, maybe we could get used to it,” say some exasperated neighbors.
Wind turbine neighbors talk about feeling a deep rhythmic rumble inside their homes. “We feel the vibrations over the TV set,” they say. That is the Low Frequency Noise.
Some farmers living five miles from the Lowell wind turbines talk about the side of the barn vibrating. The Nelsons, who had no choice but to sell their jewel of a farm in Lowell to Green Mountain Power due to their deteriorating health and quality of life, saw the windows in their house vibrate, and the vibrations were visible in a bowl of water on the kitchen counter.
Some neighbors experience the barometric pressure waves that hit their homes, turning the house into a drum, producing inaudible infrasound inside the home at higher levels than outside. “Imagine you are sitting at your kitchen table and are seasick, except you are not on a boat and nowhere near water,” says one former neighbor whose family became so sick[i] after living 3500 feet from the wind turbines that they abandoned their home of seventeen years.
Infrasound cannot be heard, but it has been scientifically proven by recent studies to be a component of the acoustical profile of wind turbines.[ii],[iii],[iv] The vortexing pressure waves do not dissipate and can go out for miles.
This complex acoustical profile of wind turbines creates a challenge for regulators and the experts they rely on. Typical noise control measures such as insulating the source or insulating the receptor do not work with an open air source and a receptor that experiences higher levels of infrasound inside the home than outside. And people have a right to have their windows open. Insulation does not work.
The unique noise produced by wind turbines does not create a problem for the wind industry, though. “There are no problems,” is their attitude. “It’s all in their heads,” they say. “The “nocebo effect” is at work,” they claim, alleging that people’s beliefs are making them sick. They heap ridicule on neighbors who are victimized once by the wind turbines themselves, a second time by the industry which refuses to accept responsibility, and a third time by regulators who have turned a deaf ear to the hundreds of complaints filed by Vermonters since mountaintop wind turbines began operating.
A unanimous vote by the Vermont House last year affirmed that there is a problem. The legislature directed the Vermont Public Service Board to right the wrong that has occurred.
The PSB has issued a rule that sets a night-time level of 35 dBA (audible decibels). This has resulted in a shrill response from wind proponents who absurdly claim that this standard, which is the nighttime noise standard for wind turbines in Germany, would outlaw bird songs.
Here is a short course on wind turbines and decibel levels:
- dBA is audible decibels. Nighttime background noise levels in the areas where wind turbines have been constructed are about 20 dBA. 10 dBA above background is well known to result in complaints. It is the noise standard that has been used in Massachusetts for decades. By that measure, the correct standard for wind turbines in the very quiet areas where wind turbines are being built would be 30 dBA – lower than the PSB is proposing.
- dBC is the frequency scale for Low Frequency Noise. Denmark has an interior noise standard of 20 dBC.[v]
- The best solution for protecting people from infrasound is distance. The PSB rule has a 10× total height setback, or 5000 feet for 500 foot tall wind turbines, the same as places in Germany. It may not be far enough, but it is a step in the right direction.
The wind developers have made big promises. Now they have promises to keep – so their neighbors don’t have miles to go before they sleep. And the Vermont Public Service Board should establish standards that reflect those promises.
Annette Smith is Executive Director of Vermonters for a Clean Environment, Inc. She is the Burlington Free Press’s 2016 Vermonter of the Year.
[v] http://eng.mst.dk/topics/noise/wind-turbines/wind-turbine-regulations/ [NWW note: The Danish indoor limit is 20 dBA (not dBC) for the range of 10–160 Hz]